Clutch



Dec. 12, 1950 J. E. LEININGER EAL 3 CLUTCH Filed April 25, 1945 INVEN J. E. LEINING BY. G.L.SEATON a o I ATTORNEY the manufacture of some types of clutches em- 20 which is adapted to drive a pinion shaft ll Patented Dec. 12, 1950 2,533,480

UNITED STATES PATENT, OFFICE CLUTCH James E. Leininger and Charles L. Seaton, Burbank, CaliL, asslgnors to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application April 25, 1945, Serial No. 590,134

2 Claims. (Cl. 192-101) 2 This invention relates to clutches for inter- A complete understanding of the invention may coupling two rotating members and is particularbe had from the following detailed description of ly useful in magnetic clutches. a particular embodiment thereof as disclosed in An object of the invention is to provide a clutch the drawing in which plate construction that has high holding power 5 Fig. l is a side elevation view with portions relative to the area of the friction faces and the broken away of a mechanism incorporating a force that urges the plates together. magnetic clutch to which the invention is ap- Another object is to provide a clutch plate plied. construction having good frictional characteris- Fig. 2, is an end view of one of the clutch plates, tics that can be readily manufactured. the view being taken in the plane 11-11 of Fig. l. A more specific object is to provide a clutch Fig. 3 is an end view of the other clutch plate, plate design such that the plates can be comthe view being taken in the plane III-III of pletely finished prior to assembly of the clutch Fig. 1. 1 and thereby eliminate interfltting the plates by Fig. 4 is a section taken in the plane IV- --IV the process of wearing them in after assembly. 15 of Fig. 2; and

Other more specific objects and features of the Fig. 5 is a section taken in the plane V--V of invention will appear from the detailed de- Fig. 3. I scription to follow. Referring first to Fig. 1, there is disclosed a Heretofore, it has been'considered necessary in mechanism incorporating an electric motor l0 ploying interengaging metallic plates to fit the through a magnetic clutch incorporating the plates together after assembly by a process represent invention. The pinion shaft H carries ferred to as burning in, which involves the gear teeth I2 on its end meshing with a. driven slipping of the plates with respect to each other gear [3 but the mechanism driven by the pinion until their surfaces are. worn to correspond to 25 shaft ll does not constitute a part of the present each other and effect contact over substantially invention. their entire areas. This process is objectionable Motor III has a shaft M which is supported by not only because considerable time is required to a ball bearing l5 mounted in a wall l6, shaft l4 complete the buming in process, but because extending through the bearing and having in many instances it fails to produce surfaces 0 mounted on its outer end a driving clutch plate having suflicient friction to transmit the reassembly I! which consists of a hub [8 formed quiredtorque. Nevertheless, prior to the present integrally with a flange 19 which constitutes the invention, the burning in" process was the only driving plate of the clutch. The clutch assembly known way of producing the desired frictional l! is secured to the shaft l4 by a pin 20 and is characteristics between the clutch plates. 35 rotatably supported against longitudinal move- In accordance with the present invention, we ment by the bearing IS. The clutch assembly I1 eliminate the necessity of "buming in" the clutch is made of steel or other paramagnetic material. plate surfaces by grinding the faces of the plates The pinion shaft H is rotatably supported by on the side of a grinding wheel to produce the a ball bearing 2|, the bearing comprising an necessary contour of the faces and, at the same inner race 22 mounted on the shaft ll, balls 23 time, provide a finish having high frictional charand an outer race 24. The outer race 24 has a acteristics with respect to the cooperating plate. cylindrical outer surface which is slidably fitted By grinding the faces of the plates on the side within a stationary sleeve 25 in a clutch casing of the grinding wheel, the fine striae or lines 26. Formed integrally with the shaft H on its produced by the wheel on the ground surface are inner end is a hub 21, which hub has at its inner caused to extend diagonally across the plates with edge an outwardly extending flange 21} which a radial component, whereas when two plates are forms the driven clutch plate. burned in, the striae extend circumferentially. The entire assembly, including the driven It has been found by experiment that when the clutch plate 28 and the bearing 2| is slidable plates are ground so that the striae have a radial longitudinally in the sleeve 25 to engage and component as described, that the friction between disengage the clutch. As shown in Fig. 1, the the plates is greatly increased and is much more clutch is disengaged, in which position the driven uniform in-quantity production than in plates plate is moved out of contact with the driving that have been produced by the burning in" plate i9 by a helical spring 29 which is interposed D between a stationary shoulder 30 forming a part of the casing and the outer race 24 of the bearing 2 I. The shoulder 30 is formed on the inner edge of an annular plate 32 which is secured to the casing 28 by screws 33 and has an annular brake lining 3| on its inner face against which the rear face of plate 28 abuts in disengaged position. Friction between the brake lining 34 and the plate 28 quickly stops rotation of th plate when the clutch is disengaged.

The clutch is engaged by magnetic force. To this end, an energizing winding 36 is provided surrounding the hub l8 of the drivingv clutch member. The winding 36 is supported by a frame 38 extending from the wall l6.

As previously indicated, the driving plate assembly I1 is of steel or other paramagnetic material. Likewise, the driven plate assembly including the hub 21 and the plate 28 are of steel or other paramagnetic material, although one or the other of the clutch plates may have a nonmagnetic surface layer to improve the frictional characteristics. When the winding 36 is energized, the hub l8 of the driving assembly I! is strongly magnetized and strongly attracts the hub 21 on the driven clutch member. The magnetic force is far in excess of that offered by the spring 29, so that the entire assembly including the pinion shaft II, the bearing 2|; the hub 21, and the plate 28 is moved to the right until the face of the plate 28 engages the face of the plate I9. These faces are supposed to engage each other with sufficient friction to transmit the motion of the motor shaft H to the pinion shaft II without slippage, but heretofore some difficulty has been encountered in providing the necessary friction between the clutch-elements to avoid slippage. The best prior-known method of preventing slippage in use was to burn the surfaces of the plates l8 and 28 together until they interfitted over substantially their entire area. However, this required considerable time and there were many rejects.

In accordance with the present invention, the surfaces of the driving and driven members are ground to predetermined shape prior to assembly of the clutch and no burning in" is employed.

Referring to Fig. 4, the driven plate 28 has its working face 38 ground substantially fiat and the grinding. is done either on the side of a straight grinding wheel or the face of a cup-type grinding wheel to produce a finish having striae extending at an angle across the annular surface 38 as indicated by the lines 40 in Fig. 2.

The driving plate I9 is likewise finished on the side of a straight grinding wheel or on the face of a cup-type grinding wheel to produce a finish in which the grinding striae ll (Fig. are complementary to the striae 40 on the driven plate. The driving member I9, however, is ground to produce a dish. that is, the outer edge of the clutch surface is higher than the inner diameter. This is done because it is found that when the plates are urged together by the magnetic force, they are slightly distorted, so that if both plates were initially ground fiat, contact would be had only along the inner diameter of the surface 38 when the plates are forced together. Jlfhis would result in burning, in service. The amount of dish imparted to the driving plate I! depends upon the rigidity of the driving and driven plates, and upon the magnetic force that is developed. The proper dish can be determined by experiment for any particular combination of driving and driven plates and any particular magnetic force that is developed, In

a clutch in which the maximum diameter of the plates is 1 and in which the plates are approximately 5" in thickness, with other proportions as indicated in Figs. 4 and 5, it is found that the amount of dish should amount to between .0010" and .0015" measured at the shoulder 42 in Fig. 5. The dish" is greatly exaggerated in Fig. 5 to make it visible.

As has been previously indicated, one of the surfaces preferably has a coating of a different material, and in Fig. 4 such a coating is shown in the surface 38 of the driven plate. This coating may be of sintered bronze and divided into four quadrants as shown in Fig. 2 with small radial grooves 44 between the quadrants which permits any dust formed by friction between the clutch members to be thrown out by centrifugal force.

If the grinding of the surfaces is done on a wheel of substantial diameter, the striae lines 40 and 4| (Figs. 2 and 3) will appear substantially straight instead of arcuate. However, they always have a slight curvature and it is preferred that the curvatures be in opposite directions as viewed in Figs. 2 and 3 so that when the members are brought together, the lines on one member coincide with lines of the other which will produce the maximum friction between the members. However, it is understood that even though the grinding lines or striae on the two members are not exactly registered when the members are brought together, the friction is substantially higher than on members that are finished by burning them in. In the latter case, the surface finish lines or striae are in the form of circles centered about the axis of rotation of the clutch.

It has been found satisfactory in practice to grind the faces of the plates with a Norton grinding wheel No. 46M5B2 having a surface speed of 6500 feet per minute, while rotating the plate at from to 200 R. P. M. If the grinding lines or striae are either too coarse or too fine, the holding power is decreased, and the optimum texture in any given case can be determined by experiment.

It is to be noted that when one of the faces of the clutch is provided with a coating of non-magnetic material, such as sintered bronze, there is no direct contact between two magnetic materials when the clutch is engaged, and hence there is no tendency for the clutch to stick. The dished surface of the driving member I9 is not for the purpose of overcoming residual magnetism between the members, but to enable the parts to be preground and yet fit over their entire areas when the clutch is engaged despite distortion of one or both of the clutch members.

The present invention relates to clutches in which some slippage is intended for the purpose of accelerating the driven member smoothly and without shock, as distinct from clutches of the type intended to provide instantaneous engagement. In the claims the expression slip-type" is intended to distinguish from the instantaneous type of clutch without signifying a clutch that slips continuously at all times.

We claim:

1. A slip type clutch comprising: a pair of axially alined rotary driving and driven elements adapted for relative axial movement into and out of frictional engagement with each other in which both of said elements have cooperating, substantially smooth, ground annular friction surfaces having curved grinding striae extending thereacross in a direction having a radial component,

5 said striae being of such curvature and degree of ,ilneness as to provide substantially maximum together.

JAMES E. LEININGER. CHARLES L. SEATON.

REFERENCES CITED The following references are of record in the file of this patent:

Number Number 6 UNITED STATES PATENTS Name Date Zimmerman Feb. 27, 1912 Newdick Sept. 7, 1926 Grossbard Nov. 8, 1927 Lane Feb. 21, 1933 Winkler May 25, 1937 Ojutkangus Apr. 16, 1946 FOREIGN PATENTS Country Date Great Britain Feb. 9, 1923 

